The stem connects the handlebars to the bike. Stems are available in different versions and sizes. The two most common types are A-head and quill. Quill stems are more common in standard e-bikes, and run down through the opening of the front fork, which is placed inside the frame’s head tube (the front tube). To attach the stem, a bolt on the top of it is tightened, expanding a metal object at the bottom of the stem and preventing it from slipping out of the tube. In e-bikes with A-head stems, the front fork runs through the head tube, ending a little above the top edge of the head tube. The A-head stem is threaded over the front fork and fixed with a locking mechanism.